This application is in response to a program announcement for high-risk/high-impact research. The objective of the proposed research is to determine whether nicotinic adenine dinucleotide phosphate (NAADP) is a mediator of calcium mobilization in mammalian systems. NAADP is a metabolite of beta- nicotinamide adenine dinucleotide 2'-phosphate (beta-NADP) that has been found to mobilize calcium from intracellular stores in sea urchin eggs. This occurs by a mechanism distinct from those mediated by IP3 or cyclic ADP-ribose. NAADP signaling has not been demonstrated in mammalian cells, although the enzymes necessary to synthesize and degrade NAADP are present and preliminary data suggests that NAADP may occur in mammalian cells. The following specific aims address the question of whether NAADP signaling is operational in mammalian cells. 1) Does NAADP occur in mammalian cells? 2) Are NAADP binding proteins detectable in mammalian cells? 3) Can NAADP induce calcium release in mammalian systems? These studies propose to identify a new Ca signaling pathway in mammalian cells, with important implications for our understanding of calcium ion mobilization.